The present invention relates to an internal-combustion engine, and more particularly, to a four-stroke IC engine comprising three intake valves and one exhaust valve per cylinder actuated by camshafts arranged in a cylinder head and acting, via associated valve disks, upon valve openings of a combustion chamber, the valve openings having different diameters from each other and valve opening centers situated on both sides of a longitudinal center plane.
Internal-combustion engines having a multiple valve arrangement per cylinder, that is, more than one intake valve and exhaust valve, are well known. For example, German Patent DE-OS 28 38 681 uses two intake valves and one exhaust valve per cylinder combustion chamber, whereby one intake valve operates in the partial-load range and the other intake valve operates in the remaining load range.
European Patent EP 0 063 3851 B1 shows a four-stroke internal-combustion engine in which three intake valves and two exhaust valves operate in its respective combustion chamber by way of which the load per se and the load change during the operation of the internal-combustion engine are intended to be improved.
Furthermore, the construction shown in German Patent Document DE 37 24 495 A1 provides three intake valves and one exhaust valve per cylinder. The mixture is ignited by two spark plugs. This construction is intended to achieve a high volumetric efficiency with a good output.
It is an object of the present invention to provide a multivalve arrangement for an advanced-design, four-stroke internal-combustion engine which, while using three intake valves and one exhaust valve, improves the operation of this internal-combustion engine with respect to fuel consumption and exhaust gas emission while maintaining good output and high torque, and ensuring that the constructional expenditures are within acceptable limits.
This object has been achieved according to the present invention by providing that the intake valves and exhaust valve of each cylinder are arranged such that the valve opening centers of the valve openings of first and second valves of the intake valves are situated on one side of the longitudinal center plane, whereas the valve opening centers of the valve openings of the third intake valve and of the exhaust valve are situated on another side of the longitudinal center plane.
The principal advantages achieved with the present invention are that the three intake valves and the exhaust valve represent, an optimum construction between three-valve technology (two intake valves, one exhaust valve) and five-valve technology (three intake valves, two exhaust valves). The multivalve configuration of the present invention requires only two preexisting camshafts.
It is important feature of the present invention that the third intake valve is arranged on the side of the exhaust valve which leads to a desired fast heating of the suction pipe connected with this partial-load valve. In other words, the above-mentioned valve arrangement is a recognition of the advantages of combining the cross-flow principle and the uni-flow principle in the cylinder head.
Because of its clear and simple concept, the valve arrangement of the present invention is also easily implemented in ongoing internal-combustion engine developments. In addition, the first intake valve and the second intake valve are constructed to be controllable by control elements which may, for example, be hydraulic tappets connected between the camshaft and these intake valves, as described in European Patent PCT/EP92/00502. As a result, the power, the torque, the consumption and the exhaust emission of the internal-combustion engine may be influenced in a favorable manner. The construction of the present invention takes place in connection with separate suction pipes for the first and the second intake valve or the third intake valve, in which case the suction pipe of the third intake valve can be integrated into the cylinder head cover at least in sections.
Finally, the four valves are arranged in the combustion chamber such that advantageous conditions are created from the point of view of space, also in connection with mutually separate suction pipes.